Method, user equipment and base station for determining precoding matrix indicator

ABSTRACT

The present disclosure discloses a method, a user equipment and a base station for determining a PMI. The method includes: receiving a reference signal set sent by a base station; based on the reference signal set, selecting a precoding matrix from a codebook, the codebook at least including a non-constant modulus precoding matrix, the non-constant modulus precoding matrix at least including a non-constant modulus column vector, amplitude values of at least two elements of the non-constant modulus column vector forming a symmetrical sequence; and sending a PMI to the base station, the PMI corresponding to the selected precoding matrix. According to the method, the user equipment and the base station for determining PMI, because the non-constant modulus precoding matrix included in the adopted codebook can adjust the shape of a beam, antennas may focus power on a hotspot region, and thus a load balance may be effectively realized.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2012/078020, filed on Jul. 2, 2012, which is hereby incorporatedby reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the field of communications, and inparticular, to methods, user equipments and base stations fordetermining a precoding matrix indicator.

BACKGROUND

Through a transmit beamforming (Beam Forming, “BF” for short) orprecoding technology, a multiple input multiple output (Multiple InputMultiple Output, “MIMO” for short) wireless system may obtain diversityand array gain. A typical system using BF or precoding generally may bedenoted as y=HWs+n, wherein y is a received signal vector, H is achannel matrix, W is a precoding matrix, s is a transmitted signalvector, and n is a measurement noise and interference.

An optimal precoding generally needs a transmitter to completely knowchannel state information (Channel State Information, “CSI” for short).As in a common method, a user equipment (User Equipment, “UE” for short)quantizes instantaneous CSI and feeds back the quantized CSI to a basestation (evolved Node B, eNB). The CSI information fed back in theexisting long term evolution (Long Term Evolution, “LTE” for short)release 8 (Release 8, “R8” for short) system includes a rank indicator(Rank Indicator, “RI” for short), a precoding matrix indicator(Precoding Matrix Indicator, “PMI” for short) and channel qualityindicator (Channel Quality Indicator, “CQI” for short) etc, wherein theRI and the PMI indicate the number of layers and a precoding matrix usedrespectively. Generally, a set of precoding matrices is referred to as acodebook or a precoding codebook, and each precoding matrix in thecodebook is referred to as a code word.

To reduce system cost, achieve higher system capacity and meet coveragerequirement meanwhile, an active antenna system (Active Antenna System,“AAS” for short) is already widely deployed in practice. AAS is beingconsidered to be introduced into an LTE release 12 (Release 12, “R12”for short) standard to be started at present, so as to enhance thecommunication performance of the system. In AAS (AAS) system, atransceiver is directly connected with antenna elements, and theamplitude and phase of each antenna element may be directly adjusted, sothat not only beam direction but also beam shape can be adjusted.

With the development of data services, particularly the appearance of ahotspot region in a heterogeneous network, a network system is requiredto adapt to a unbalanced network load. For example, better power isprovided for the hotspot region, etc. The AAS provides a beneficialmanner for solving the load imbalance issues, so as to focus the poweron the hotspot region and reduce the interference on a non-hotspotregion at the same time.

However, the present LTE R8 system adopts a single codebook, wherein the4-antenna codebook is designed on the basis of a Householdertransformation, and each element of a precoding matrix in the codebookhas the same amplitude, namely satisfies constant modulus property, sothat the precoding matrix can only adjust the beam direction but can notadjust the beam shape. LTE release 10 (Release 10, “R10” for short)system further introduces a double-codebook design for 8 antennas, butthe precoding matrix included in double codebooks can also only adjustbeam direction but can not adjust beam shape.

Therefore, the above-mentioned codebooks can not enable a communicationsystem to realize a load balance.

SUMMARY

Embodiments of the present disclosure provide methods, user equipmentsand base stations for determining a precoding matrix indicator. Anon-constant modulus precoding matrix included in an adopted codebookcan adjust beam shape, so that a communication system may effectivelyrealize a load balance.

In one aspect, an embodiment of the present disclosure provides a methodfor determining a precoding matrix indicator, including: receiving areference signal set sent by a base station; based on the referencesignal set, selecting a precoding matrix from a codebook, the codebookat least including a non-constant modulus precoding matrix, thenon-constant modulus precoding matrix at least including a non-constantmodulus column vector, amplitude values of elements of the non-constantmodulus column vector forming a symmetrical sequence, and a length ofthe sequence being not smaller than 2 and not greater than the number ofdimensions of the non-constant modulus column vector; and sending aprecoding matrix indicator to the base station, the precoding matrixindicator corresponding to the selected precoding matrix.

In another aspect, an embodiment of the present disclosure provides amethod for determining a precoding matrix indicator, including: sendinga reference signal set to a user equipment; receiving a precoding matrixindicator sent by the user equipment, the precoding matrix indicatorcorresponding to a precoding matrix selected from a codebook by the userequipment based on the reference signal set, the codebook at leastincluding a non-constant modulus precoding matrix, the non-constantmodulus precoding matrix at least including a non-constant moduluscolumn vector, amplitude values of elements of the non-constant moduluscolumn vector forming a symmetrical sequence, and a length of thesequence being not smaller than 2 and not greater than the number ofdimensions of the non-constant modulus column vector.

In a further aspect, an embodiment of the present disclosure provides auser equipment, including: a receiving module, configured to receive areference signal set sent by a base station; a selecting module,configured to, based on the reference signal set received by thereceiving module, select a precoding matrix from a codebook, thecodebook at least including a non-constant modulus precoding matrix, thenon-constant modulus precoding matrix at least including a non-constantmodulus column vector, amplitude values of elements of the non-constantmodulus column vector forming a symmetrical sequence, and a length ofthe sequence being not smaller than 2 and not greater than the number ofdimensions of the non-constant modulus column vector; and a sendingmodule, configured to send a precoding matrix indicator to the basestation, the precoding matrix indicator corresponding to the precodingmatrix selected by the selecting module.

In a still further aspect, an embodiment of the present disclosureprovides a base station, including: a sending module, configured to senda reference signal set to a user equipment; a receiving module,configured to receive a precoding matrix indicator sent by the userequipment, the precoding matrix indicator corresponding to a precodingmatrix selected from a codebook by the user equipment based on thereference signal set, the codebook at least including a non-constantmodulus precoding matrix, the non-constant modulus precoding matrix atleast including a non-constant modulus column vector, amplitude valuesof elements of the non-constant modulus column vector forming asymmetrical sequence, and a length of the sequence being not smallerthan 2 and not greater than the number of dimensions of the non-constantmodulus column vector.

Based on the above technical solutions, according to the methods, theuser equipments and the base stations for determining the precodingmatrix indicator provided in the embodiments of the present disclosure,the precoding matrix is determined from the codebook with thenon-constant modulus precoding matrix, and the non-constant modulusprecoding matrix has the non-constant modulus column vector of which theamplitude values of the elements are symmetrical or partiallysymmetrical, so that the non-constant modulus precoding matrix mayadjust beam shape, antennas can focus power on a hotspot region, thus aload balance of the communication system may be effectively realized andthe performance of the communication system may be improved.

BRIEF DESCRIPTION OF DRAWINGS

To illustrate the technical solutions provided in the embodiments of thepresent disclosure more clearly, a brief introduction on theaccompanying drawings which are needed in the description of theembodiments will be given below. Apparently, the accompanying drawingsin the description below are merely some of the embodiments of thepresent disclosure, based on which other drawings may be obtained bythose skilled in the art without any inventive efforts.

FIG. 1 is a schematic flow diagram of a method for determining aprecoding matrix indicator according to an embodiment of the presentdisclosure.

FIG. 2 is a schematic flow diagram of a method for determining aprecoding matrix indicator according to another embodiment of thepresent disclosure.

FIG. 3 is a schematic block diagram of a user equipment according to anembodiment of the present disclosure.

FIG. 4 is a schematic block diagram of a base station according to anembodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

A clear and complete description of technical solutions provided in theembodiments of the present disclosure will be given below, inconjunction with the accompanying drawings in the embodiments of thepresent disclosure. Apparently, the embodiments described below aremerely a part, but not all, of the embodiments of the presentdisclosure. All of other embodiments, obtained by those skilled in theart based on the embodiments of the present disclosure without anyinventive efforts, fall into the protection scope of the presentdisclosure.

It should be understood that, the technical solutions of the embodimentsof the present disclosure may be applied to various communicationsystems, such as a global system of mobile communication (Global Systemof Mobile communication, “GSM” for short), a code division multipleaccess (Code Division Multiple Access, “CDMA” for short) system, awideband code division multiple access (Wideband Code Division MultipleAccess, “WCDMA” for short) system, a general packet radio service(General Packet Radio Service, “GPRS” for short) system, a long termevolution (Long Term Evolution, “LTE” for short) system, an LTEfrequency division duplex (Frequency Division Duplex, “FDD” for short)system, an LTE time division duplex (Time Division Duplex, “TDD” forshort) system, a universal mobile telecommunication system (UniversalMobile Telecommunication System, “UMTS” for short), a worldwideinteroperability for microwave access (Worldwide Interoperability forMicrowave Access, “WiMAX” for short) communication system and the like.

It should also be understood that, in the embodiments of the presentdisclosure, a user equipment (User Equipment, “UE” for short) may bereferred to as a terminal (Terminal), a mobile station (Mobile Station,“MS” for short), a mobile terminal (Mobile Terminal) and the like, andmay communicate with one or more core networks through a radio accessnetwork (Radio Access Network, “RAN” for short). For example, the userequipment may be a mobile phone (or referred to as a “cell” phone), acomputer with a mobile terminal. For example, the user equipment mayalso be a portable, pocket-type, handheld, computer built-in orvehicle-mounted mobile device. The user equipment exchanges voice and/ordata with the radio access network.

In the embodiments of the present disclosure, the base station may be abase transceiver station (Base Transceiver Station, “BTS” for short) inGSM or CDMA, or a NodeB (NodeB, “NB” for short) in WCDMA, or an evolvedNodeB (Evolved Node B, “eNB or e-NodeB” for short) in LTE, which is notlimited in the present disclosure. For the purpose of convenience indescription, the eNB is taken as an example for illustrating in thefollowing embodiments.

FIG. 1 shows a method 100 for determining a precoding matrix indicatoraccording to an embodiment of the present disclosure. The method 100 maybe executed by a user equipment, for example, executed by a UE. Themethod 100 includes:

S110, receiving a reference signal set sent by a base station;

S120, based on the reference signal set, selecting a precoding matrixfrom a codebook, the codebook at least including a non-constant modulusprecoding matrix, the non-constant modulus precoding matrix at leastincluding a non-constant modulus column vector, and amplitude values ofat least two elements of the non-constant modulus column vector forminga symmetrical sequence;

S130, sending a precoding matrix indicator to the base station, theprecoding matrix indicator corresponding to the selected precodingmatrix.

Therefore, according to the method for determining the precoding matrixindicator provided in the embodiment of the present disclosure, theprecoding matrix is determined from the codebook with the non-constantmodulus precoding matrix, and the non-constant modulus precoding matrixhas the non-constant modulus column vector of which the amplitude valuesof the elements are symmetrical or partially symmetrical, so that thenon-constant modulus precoding matrix may adjust beam shape, thus anantenna can focus power on a hotspot region, a load balance of acommunication system may be effectively realized, and the performance ofthe communication system may be improved.

On the other hand, according to the method for determining the precodingmatrix indicator provided in the embodiment of the present disclosure,the user equipment feeds back one or more precoding matrix indicatorsfor indicating the precoding matrix based on the reference signal set,so that the channel correlation in time domain, frequency domain orspatial domain may be fully utilized, thus the feedback overhead may beremarkably reduced, and the performance of the communication system maybe further improved.

In S110, the user equipment receives the reference signal set sent bythe base station.

Specifically, the user equipment may receive a notification sent by thebase station through high layer signaling or through a downlink controlchannel, the notification includes the reference signal set, and thusthe user equipment can receive the reference signal set sent by the basestation. For example, the base station may send the reference signal setto the user equipment through radio resource control (Radio ResourceControl, “RRC” for short) signaling, or through a physical downlinkcontrol channel (Physical Downlink Control Channel, “PDCCH” for short),or through an enhanced PDCCH (enhanced PDCCH, “ePDCCH” for short).

The reference signal set may include one or more reference signals, andthe reference signals may be cell-specific reference signals(Cell-specific Reference Signal, “CRS” for short) or channel stateinformation-reference signals (Channel State Information-ReferenceSignal, “CSI-RS” for short).

It should be understood that, the reference signals may also be otherreference signals, but the embodiments of the present disclosure are notlimited thereto. It should also be understood that, in the embodiment ofthe present disclosure, the user equipment receiving the referencesignal set sent by the base station may also be understood as the userequipment acquiring a reference signal port set.

In S120, the user equipment selects the precoding matrix from thecodebook based on the reference signal set. The codebook at leastincludes a non-constant modulus precoding matrix, the non-constantmodulus precoding matrix at least includes a non-constant modulus columnvector, the amplitude values of part of elements or all of elements ofthe non-constant modulus column vector form a symmetrical sequence, andthe length of the sequence is not smaller than 2 and not greater thanthe number of dimensions of the non-constant modulus column vector. Thecodebook will be described in detail below.

It is supposed that the non-constant modulus precoding matrix W at leastincluded in the codebook has a structure as shown in the equation (1):

[w ₁ w ₂ . . . w _(r)]  (I)

Wherein, w_(j) denotes the j^(th) column vector of the non-constantmodulus precoding matrix W, j is a natural number and 1≦j≦r, and r isthe rank or the number of columns of the non-constant modulus precodingmatrix W. It should be understood that, a constant modulus precodingmatrix denotes a precoding matrix of which elements have the sameamplitude; and the non-constant modulus precoding matrix denotes aprecoding matrix of which not all elements have the same amplitude,namely in the non-constant modulus precoding matrix, at least oneelement has an amplitude different from the amplitudes of otherelements.

The non-constant modulus precoding matrix W at least includes anon-constant modulus column vector w_(s), s is a natural number and1≦s≦r, and it is supposed that the non-constant modulus column vectorw_(s) has a structure as shown in the following equation (2):

$\begin{matrix}{w_{s} = \left\lbrack {a_{1\; s}^{j\; \theta_{1\; s}}\mspace{14mu} a_{2\; s}^{j\; \theta_{2\; s}}\mspace{14mu} \ldots \mspace{14mu} a_{{({t - 1})}s}^{j\; \theta_{{({t - 1})}s}}\mspace{14mu} a_{ts}^{j\; \theta_{ts}}} \right\rbrack^{T}} & (2)\end{matrix}$

Wherein, [ ]^(T) denotes the transposition operation of a matrix or avector, α_(ks) and θ_(ks) are respectively the amplitude and phase ofthe k^(th) element of the non-constant modulus column vector w_(s), k isa natural number and 1≦k≦t, and t is the number of dimensions of thenon-constant modulus column vector w_(s), namely the number of rows ofthe non-constant modulus precoding matrix W. Moreover, the phase inequation (2) may be derived from the phase of a precoding matrixdesigned in an existing constant modulus precoding codebook, forexample, a codebook with 4 antennas or 8 antennas in the existing LTEsystem, which is not further redundantly described herein.

The amplitude values of all of or part of elements of the non-constantmodulus column vector w_(s) may form at least one symmetrical sequenceA, and it is supposed that the sequence A has a structure as shown inthe equation (3):

A={a ₁ ,a ₂ , . . . ,a _(M)}(a _(i) εB)  (3)

Wherein, a_(i) is the i^(th) element amplitude value of the sequence A,and i is a natural number and 1≦i≦M; the set B is a set formed by theamplitude values of the elements of the non-constant modulus columnvector w_(s); M is the length of the sequence, M is a natural number and2≦M≦t; and t is the number of the elements of the set B.

Then, the symmetrical sequence A means that the sequence A satisfies thefollowing equation (4) or (5):

a ₁ =a _(M) ,a ₂ =a _(M−1) , . . . ,a _(M/2) =a _((M/2)+1)(M iseven)  (4)

a ₁ =a _(M) ,a ₂ =a _(M−1) , . . . ,a _((M−1)/2) =a _((M+3)/2)(M isodd)  (5)

In the embodiment of the present disclosure, the non-constant modulusprecoding matrix W may include one above-mentioned non-constant moduluscolumn vector w_(s) or two or more above-mentioned non-constant moduluscolumn vectors w_(s). Alternatively, the codebook at least includes anon-constant modulus precoding matrix, each column vector of thenon-constant modulus precoding matrix is a non-constant modulus columnvector, the amplitude values of elements of each non-constant moduluscolumn vector form a symmetrical sequence, and the length of thesequence is not smaller than 2 and not greater than the number ofdimensions of the non-constant modulus column vector.

In the embodiment of the present disclosure, the amplitude values of allelements of the above-mentioned non-constant modulus column vector mayform a symmetrical sequence. For example, a sequence formed by theamplitude values of the elements of the non-constant modulus columnvector w_(s) in row order may have symmetrical property; and a sequenceformed by the amplitude values of the elements of the non-constantmodulus column vector w_(s), after row permutation, may have symmetricalproperty.

For example, for a 6-dimensional non-constant modulus column vectorw_(s1), the amplitude values of which may form a sequence A1={1, 3, 2,2, 3, 1} in row order, and the sequence A1 has symmetrical property.Thus, by adopting the precoding matrix including the non-constantmodulus column vector, the distribution of power or energy of antennasmay be adjusted, so that the power may be effectively focused on ahotspot region, and thus a load balance may be realized.

For another example, for a 6-dimensional non-constant modulus columnvector w_(s2), the amplitude values of which may form a sequence {1, 2,3, 2, 3, 1} in row order, and a symmetrical sequence A1 may be formedaccording to a exchanged row order, after the 2^(nd) row of thenon-constant modulus column vector w_(s1) is exchanged with the 3^(rd)row. Similarly, by adopting the precoding matrix including thenon-constant modulus column vector, the distribution of power or energyof antennas may be adjusted, so that the power may be effectivelyfocused on a hotspot region, and thus a load balance may be realized.

In the embodiment of the present disclosure, the amplitude values ofpart of elements of the above-mentioned non-constant modulus columnvector may also form a symmetrical sequence, for example, the sequenceformed by the amplitude values of part of elements of the non-constantmodulus column vector w_(s) in row order or through row permutation mayhave symmetrical property.

For example, for a 7-dimensional non-constant modulus column vectorw_(s3), the sequence formed by the amplitude values of the vector in roworder is {1, 3, 2, 2, 3, 1, 1.5}, and the amplitude values of part ofelements of the vector may form a symmetrical sequence A1; for a7-dimensional non-constant modulus column vector w_(s4), the sequenceformed by the amplitude values of the vector in row order is {1, 2, 3,2, 3, 1, 1.5}, and the amplitude values of part of elements of thevector may also form a symmetrical sequence A1 after row permutation.Thus, by adopting the precoding matrix including the non-constantmodulus column vector w_(s3) or w_(s4), the distribution of power orenergy of antennas may be adjusted, so that the power may be effectivelyfocused on a hotspot region, and a load balance may also be realized.

In the embodiment of the present disclosure, alternatively, the codebookat least includes a non-constant modulus precoding matrix, thenon-constant modulus precoding matrix at least includes a non-constantmodulus column vector, the amplitude values of the elements of thenon-constant modulus column vector may be divided into at least twosets, the amplitude values of the elements of each of the at least twosets may form a symmetrical sequence, and the length of the sequence isnot smaller than 2 and not greater than the number of dimensions of thenon-constant modulus column vector.

For example, for a non-constant modulus column vector w_(s5), thesequence formed by the amplitude values of the vector in row order is{1, 1.5, 3, 2, 1, 1.5, 1, 2}, the amplitude values of the elements ofthe non-constant modulus column vector may be divided into at least twosets B1 and B2, e.g. B1={1, 2, 3, 2, 1}, B2={1.5, 1, 1.5}. The sets B1and B2 may form symmetrical sequence A2 and A3 respectively, whereinA2={1, 2, 3, 2, 1}, and A3={1.5, 1, 1.5}. Similarly, by adopting theprecoding matrix including the non-constant modulus column vectorw_(s5), the distribution of power or energy of antennas may be adjusted,so that the power may be effectively focused on a hotspot region, and aload balance may also be realized.

Further, in the embodiment of the present disclosure, the amplitudevalues of the elements of the above-mentioned non-constant moduluscolumn vector may be selected from a finite set, for example, theamplitude values of the elements are the products of the amplitudes ofknown modulation symbols (such as modulation symbols in 16QAM or 64QAMor 256QAM) and a common factor. The above-mentioned selection may reducethe implementation complexity that the UE selects the precoding matrix.

In S130, the user equipment sends the precoding matrix indicatorcorresponding to the selected precoding matrix to the base station.

Specifically, for example, the user equipment may send the precodingmatrix indicator to the base station through a physical uplink controlchannel (Physical Uplink Control Channel, “PUCCH” for short) or aphysical uplink shared channel (Physical Uplink Shared Channel, “PUSCH”for short).

It should be understood that, in the embodiment of the presentdisclosure, after the base station receives the precoding matrixindicator, the base station may determine a precoding matrix W accordingto the precoding matrix indicator and transmit a signal vector saccording to the precoding matrix W. The user equipment may determinethe signal vector s transmitted by the base station according to areceived signal, the precoding matrix W and a channel matrix H or aprecoded efficient channel HW, noise and interference n.

Therefore, according to the method for determining the precoding matrixindicator provided in the embodiment of the present disclosure, theprecoding matrix is determined from the codebook with the non-constantmodulus precoding matrix, and the non-constant modulus precoding matrixhas the non-constant modulus column vector of which the amplitude valuesof the elements are symmetrical or partially symmetrical, so that thenon-constant modulus precoding matrix may adjust beam shape, thusantennas may focus power on a hotspot region, a load balance of acommunication system may be effectively realized, and the performance ofthe communication system may be improved.

In the embodiment of the present disclosure, alternatively, the sequenceconsisting of the amplitude values of the elements of the non-constantmodulus column vector and having symmetrical property satisfies thefollowing relationship (6) or (7):

$\begin{matrix}\left\{ {\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{M/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M/2})} + 1}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {even}} \right)} \right. & (6) \\\left\{ {\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {odd}} \right)} \right. & (7)\end{matrix}$

Wherein, M is the length of the sequence; and a_(i) is the i^(th)amplitude value of the sequence, i is a natural number and 1≦i≦M.

For example, for an 8-antenna non-constant modulus precoding matrix W,the amplitude values of the elements of a non-constant modulus columnvector w_(s) included in the non-constant modulus precoding matrix W mayform a sequence A4 with symmetrical property, and A4={1, 1.5, 2, 2.5,2.5, 2, 1.5, 1}. For another example, for a 10-antenna non-constantmodulus precoding matrix W, the amplitude values of the elements of anon-constant modulus column vector w_(s) may form a symmetrical sequenceA5, and

A5={1, 1.25, 1.5, 1.75, 2, 2, 1.75, 1.5, 1.25, 1}.

For another example, the amplitude values of the elements of thenon-constant modulus column vector may be divided into at least twosets, and the amplitude values of the elements of each of the at leasttwo sets may form a sequence with symmetrical property and satisfy theabove relationship (6) or (7).

It should be understood that, in the embodiment of the presentdisclosure, alternatively, the sequence consisting of the amplitudevalues of the elements of the non-constant modulus column vector andhaving symmetrical property may also satisfy the following relationship(8) or (9):

$\begin{matrix}\left\{ {\begin{matrix}{{a_{1} \geq a_{2} \geq},\ldots \mspace{14mu},{\geq a_{M/2}}} \\{{a_{M} \geq a_{M - 1} \geq},\ldots \mspace{14mu},{\geq a_{{({M/2})} + 1}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {even}} \right)} \right. & (8) \\\left\{ {\begin{matrix}{{a_{1} \geq a_{2} \geq},\ldots \mspace{14mu},{\geq a_{{({M + 1})}/2}}} \\{{a_{M} \geq a_{M - 1} \geq},\ldots \mspace{14mu},{\geq a_{{({M + 1})}/2}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {odd}} \right)} \right. & (9)\end{matrix}$

Wherein, M is the length of the sequence; and a_(i) is the i^(th)amplitude value of the sequence, i is a natural number and 1≦i≦M.

In the embodiment of the present disclosure, alternatively, thesymmetrical sequence consisting of the amplitude values of the elementsof the non-constant modulus column includes two symmetrical parts, andeach symmetrical part is a geometric sequence or an arithmetic sequence.

Specifically, for example, the two symmetrical parts included in thesymmetrical sequence are a₁, a₂, . . . , a_(M/2) and a_(M), a_(M−1), . .. , a_((M/2)+1) respectively, wherein M is even, a₁=a_(M), a₂=a_(M−1), .. . , a_(M/2)=a_((M/2)+1);

or the two symmetrical parts included in the symmetrical sequence area₁, a₂, . . . , a_((M−1)/2) and a_(M), a_(M−1), . . . a_((M+3)/2)respectively, wherein M is odd, a₁=a_(M), a₂=a_(M−1), . . . ,a_((M−1)/2)=a_((M+3)/2).

Each symmetrical part is a geometric sequence, namely the symmetricalpart satisfies the following relationship:

$\begin{matrix}{{\frac{a_{1}}{a_{2}} = {\frac{a_{2}}{a_{3}} = {\ldots = \frac{a_{{({M/2})} - 1}}{a_{({M/2})}}}}}\left( {M\mspace{14mu} {is}\mspace{14mu} {even}} \right){or}} & (10) \\{{\frac{a_{1}}{a_{2}} = {\frac{a_{2}}{a_{3}} = {\ldots = \frac{a_{{({{({M - 1})}/2})} - 1}}{a_{({{({M - 1})}/2})}}}}}\left( {M\mspace{14mu} {is}\mspace{14mu} {odd}} \right)} & (11)\end{matrix}$

It should be understood that the common ratio of the geometric sequencemay be greater than 1, or smaller than 1, but not equal to 1.

It is easy to know that the corresponding other symmetrical part a_(M),a_(M−1), . . . a_((M/2)+1) or a_(M), a_(M−1), . . . , a_((M+3)/2) isalso a geometric sequence.

Each symmetrical part is an arithmetic sequence, namely the symmetricalpart satisfies the following relationship:

a ₁ −a ₂ ×a ₂ −a ₃ = . . . =a _((M/2)−1) −a _((M/2))(M is even)  (12)

or

a ₁ −a ₂ =a ₂ −a ₃ = . . . =a _(((M−1)/2)−1) −a _(((M−1)/2))(M isodd)  (13)

It could be understood that the common difference of the arithmeticsequence may be greater than 0, or smaller than 0, but not equal to 0.

It is easy to know that the corresponding other symmetrical part a_(M),a_(M−1), . . . , a_((M/2)+1) or a_(M), a_(M−1), . . . , a_((M+3)/2) isalso an arithmetic sequence.

In the embodiment of the present disclosure, alternatively, thenon-constant modulus precoding matrix is the product of a diagonalmatrix and a constant modulus matrix, wherein the diagonal element ofthe diagonal matrix consists of the amplitude values of elements of thenon-constant modulus column vector.

Specifically, the non-constant modulus precoding matrix W may have astructure as shown in the following equation (14):

W=DU  (14)

Wherein, D is a diagonal matrix, and the diagonal elements of thediagonal matrix consist of the amplitude values of the elements of thenon-constant modulus column vector w_(s); and U is a constant modulusmatrix.

For example, the diagonal matrix D and the constant modulus matrix U areas shown in the following equations (15)-(17) respectively:

$\begin{matrix}{D = {{diag}\begin{Bmatrix}d_{1} & d_{2} & \ldots & d_{N/2} & d_{{N/2} + 1} & d_{{N/2} + 2} & \ldots & d_{N}\end{Bmatrix}}} & (15) \\{U = \begin{bmatrix}Y & Y \\{^{j\; \phi}Y} & {{- ^{j\; \phi}}Y}\end{bmatrix}} & (16) \\{{Y = \begin{bmatrix}^{j \cdot 0} & ^{j \cdot \theta} & \ldots & ^{{j \cdot {({{N/2} - 1})}}\theta}\end{bmatrix}^{T}}{{Wherein},{\phi = {\pm \frac{\pi}{2}}},{\pm \frac{\pi}{4}},{\pm \frac{\pi}{8}},{\ldots \mspace{14mu};}}{{\theta = \frac{\pi}{32}},\frac{\pi}{16},\frac{\pi}{8},{\ldots \mspace{14mu}.}}} & (17)\end{matrix}$

Further, the diagonal element of the diagonal matrix in the equation(15) satisfies

$\begin{matrix}{{\sum\limits_{i = 1}^{\frac{N}{2}}\; d_{i}^{2}} = {\sum\limits_{i = {\frac{N}{2} + 1}}^{N}\; d_{i}^{2}}} & (18)\end{matrix}$

Through the structure of the precoding matrix in equations (15)-(18),columns of the precoding matrix are orthogonal with one another, so thatinter-layer interference may be further reduced.

It should be understood that, in each embodiment of the presentdisclosure, the index of each above-mentioned procedure does not mean anexecution sequence, and the execution order of each procedure should bedetermined by functions and internal logics thereof, rather thanlimiting the implementation procedure of the embodiment of the presentdisclosure.

Therefore, according to the method for determining the precoding matrixindicator provided in the embodiment of the present disclosure, theprecoding matrix is determined from the codebook with the non-constantmodulus precoding matrix, and the non-constant modulus precoding matrixhas the non-constant modulus column vector of which the amplitude valuesof the elements are symmetrical or partially symmetrical, so that thenon-constant modulus precoding matrix may adjust beam shape, thusantennas may focus power on a hotspot region, a load balance of acommunication system may be effectively realized, and the performance ofthe communication system may be improved.

The method for determining the precoding matrix indicator according tothe embodiment of the present disclosure is described in detail from theaspect of the user equipment above in combination with FIG. 1, and willbe described from the aspect of the base station below in combinationwith FIG. 2.

As shown in FIG. 2, a method 300 for determining a precoding matrixindicator according to an embodiment of the present disclosure may beexecuted by a base station, for example, executed by an eNB. The method300 includes:

S310, sending a reference signal set to a user equipment;

S320, receiving a precoding matrix indicator sent by the user equipment,the precoding matrix indicator corresponding to a precoding matrixselected from a codebook by the user equipment based on the referencesignal set, the codebook at least including a non-constant modulusprecoding matrix, the non-constant modulus precoding matrix at leastincluding a non-constant modulus column vector, and amplitude values ofat least two elements of the non-constant modulus column vector forminga symmetrical sequence.

Therefore, according to the method for determining the precoding matrixindicator provided in the embodiment of the present disclosure, theprecoding matrix is determined from the codebook with the non-constantmodulus precoding matrix, and the non-constant modulus precoding matrixhas the non-constant modulus column vector of which the amplitude valuesof the elements are symmetrical or partially symmetrical, so that thenon-constant modulus precoding matrix may adjust beam shape, thusantennas may focus power on a hotspot region, a load balance of acommunication system may be effectively realized, and the performance ofthe communication system may be improved.

On the other hand, according to the method for determining the precodingmatrix indicator provided in the embodiment of the present disclosure,the user equipment feeds back one or more precoding matrix indicatorsfor indicating the precoding matrix based on the reference signal set,so that the channel correlation in time domain, or frequency domain orspatial domain may be fully utilized, thus the feedback overhead may beremarkably reduced, and the performance of the communication system maybe further improved.

In the embodiment of the present disclosure, the sequence consisting ofthe amplitude values of the elements of the non-constant modulus columnvector and having symmetrical property satisfies the followingrelationship:

$\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{M/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M/2})} + 1}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {even}} \right)};{{or}\text{}\left\{ {\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {odd}} \right)} \right.}} \right.$

Wherein, M is the length of the sequence; and a_(i) is the i^(th)amplitude value of the sequence, i is a natural number and 1≦i≦M.

In the embodiment of the present disclosure, alternatively, thesymmetrical sequence consisting of the amplitude values of the elementsof the non-constant modulus column vector includes two symmetricalparts, and each symmetrical part is a geometric sequence. Specifically,for example, each symmetrical part is described in (10) or (11). Itshould be understood that the common ratio of the geometric sequence maybe greater than 1, or smaller than 1, but not equal to 1.

Alternatively, the symmetrical sequence consisting of the amplitudevalues of the elements of the non-constant modulus column vectorincludes two symmetrical parts, and each symmetrical part is anarithmetic sequence. Specifically, for example, each symmetrical part isdescribed in (12) or (13). It should be understood that the commondifference of the arithmetic sequence may be greater than 0, or smallerthan 0, but not equal to 0.

In the embodiment of the present disclosure, alternatively, thenon-constant modulus precoding matrix is the product of a diagonalmatrix and a constant modulus matrix, wherein the diagonal elements ofthe diagonal matrix consist of the amplitude values of elements of thenon-constant modulus column vector. Specifically, for example, thenon-constant modulus precoding matrix has a structure described in (14)to (18).

Further, in the embodiment of the present disclosure, the amplitudevalues of the elements of the non-constant modulus column vector may beselected from a finite set, for example, the amplitude values of theelements are the products of the amplitudes of known modulation symbols(such as modulation symbols in 16QAM or 64QAM or 256QAM) and a commonfactor. The above-mentioned selection may reduce the implementationcomplexity of the eNB precoding operation.

It should be understood that, the interaction, correlation, functionsand the like of the UE and the eNB described on the eNB side correspondto those described on the UE side, which are not redundantly describedherein for the purpose of briefness.

Therefore, according to the method for determining the precoding matrixindicator provided in the embodiment of the present disclosure, theprecoding matrix is determined from the codebook with the non-constantmodulus precoding matrix, and the non-constant modulus precoding matrixhas the non-constant modulus column vector of which the amplitude valuesof the elements are symmetrical or partially symmetrical, so that thenon-constant modulus precoding matrix may adjust beam shape, thusantennas may focus power in a hotspot region, a load balance of acommunication system may be effectively realized, and the performance ofthe communication system may be improved.

The method for determining the precoding matrix indicator according tothe embodiments of the present disclosure is described in detail abovein combination with FIG. 1 and FIG. 2, and a user equipment and a basestation according to the embodiments of the present disclosure will bedescribed in detail below in combination with FIG. 3 and FIG. 4.

FIG. 3 shows a schematic block diagram of a user equipment 500 accordingto an embodiment of the present disclosure. As shown in FIG. 3, the userequipment 500 includes:

a receiving module 510, configured to receive a reference signal setsent by a base station;

a selecting module 520, configured to, based on the reference signal setreceived by the receiving module 510, select a precoding matrix from acodebook, the codebook at least including a non-constant modulusprecoding matrix, the non-constant modulus precoding matrix at leastincluding a non-constant modulus column vector, and amplitude values ofat least two elements of the non-constant modulus column vector forminga symmetrical sequence; and

a sending module 530, configured to send a precoding matrix indicator tothe base station, the precoding matrix indicator corresponding to theprecoding matrix selected by the selecting module 520.

Therefore, according to the user equipment of the embodiment of thepresent disclosure, the precoding matrix is determined from the codebookwith the non-constant modulus precoding matrix, and the non-constantmodulus precoding matrix has the non-constant modulus column vector ofwhich the amplitude values of the elements are symmetrical or partiallysymmetrical, so that the non-constant modulus precoding matrix mayadjust beam shape, thus antennas may focus power on a hotspot region, aload balance of a communication system may be effectively realized, andthe performance of the communication system may be improved.

On the other hand, according to the method for determining the precodingmatrix indicator provided in the embodiment of the present disclosure,the user equipment feeds back one or more precoding matrix indicatorsfor indicating the precoding matrix based on the reference signal set,so that the channel correlation in time domain, frequency domain orspatial domain may be fully utilized, the feedback overhead may beremarkably reduced, and the performance of the communication system maybe further improved.

In the embodiment of the present disclosure, the selecting module 520selects the precoding matrix from the codebook, the codebook at leastincludes a non-constant modulus column vector, the non-constant moduluscolumn vector at least includes a non-constant modulus column vector,and the symmetrical sequence consisting of the amplitude values of theelements of the non-constant modulus column vector satisfies thefollowing relationship:

$\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{M/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M/2})} + 1}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {even}} \right)};{{or}\text{}\left\{ {\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {odd}} \right)} \right.}} \right.$

Wherein, M is the length of the sequence; and a_(i) is the i^(th)amplitude value of the sequence, i is a natural number and 1≦i≦M.

In the embodiment of the present disclosure, alternatively, the sequenceconsisting of the amplitude values of the elements of the non-constantmodulus column vector and having symmetrical property includes twosymmetrical parts, and each symmetrical part is a geometric sequence.Specifically, for example, each symmetrical part is described in (10) or(11). Specifically, for example, each symmetrical part is described in(12) or (13). It should be understood that the common ratio of thegeometric sequence may be greater than 1, or smaller than 1, but notequal to 1.

Alternatively, the sequence consisting of the amplitude values of theelements of the non-constant modulus column vector and havingsymmetrical property includes two symmetrical parts, and eachsymmetrical part is an arithmetic sequence. Specifically, for example,each symmetrical part is described in (12) or (13). It should beunderstood that the common difference of the arithmetic sequence may begreater than 0, or smaller than 0, but not equal to 0.

In the embodiment of the present disclosure, alternatively, thenon-constant modulus precoding matrix is the product of a diagonalmatrix and a constant modulus matrix, wherein the diagonal element ofthe diagonal matrix consists of the amplitude values of elements of thenon-constant modulus column vector. Specifically, for example, thenon-constant modulus precoding matrix has a structure described in (14)to (18).

Further, in the embodiment of the present disclosure, the amplitudevalues of the elements of the non-constant modulus column vector may beselected from a finite set, for example, the amplitude values of theelements are the products of the amplitudes of known modulation symbols(such as modulation symbols in 16QAM or 64QAM or 256QAM) and a commonfactor. The above-mentioned selection may reduce the implementationcomplexity of the eNB precoding operation.

The user equipment 500 according to the embodiment of the presentdisclosure may correspond to the UE in the embodiment of the presentdisclosure, and the above-mentioned and other operations and/orfunctions of modules in the user equipment 500 are to realize thecorresponding flow of the method 100 in FIG. 1, which is not redundantlydescribed herein for the purpose of briefness.

Therefore, according to the user equipment of the embodiment of thepresent disclosure, the precoding matrix is determined from the codebookwith the non-constant modulus precoding matrix, and the non-constantmodulus precoding matrix has the non-constant modulus column vector ofwhich the amplitude values of the elements are symmetrical or partiallysymmetrical, so that the non-constant modulus precoding matrix mayadjust beam shape, thus antennas may focus power on a hotspot region, aload balance of a communication system may be effectively realized, andthe performance of the communication system may be improved.

FIG. 4 shows a schematic block diagram of a base station 700 accordingto an embodiment of the present disclosure. As shown in FIG. 4, the basestation 700 includes:

a sending module 710, configured to send a reference signal set to auser equipment;

a receiving module 720, configured to receive a precoding matrixindicator sent by the user equipment, the precoding matrix indicatorcorresponding to a precoding matrix selected from a codebook by the userequipment based on the reference signal set, the codebook at leastincluding a non-constant modulus precoding matrix, the non-constantmodulus precoding matrix at least including a non-constant moduluscolumn vector, and amplitude values of at least two elements of thenon-constant modulus column vector forming a symmetrical sequence.

In the embodiment of the present disclosure, alternatively, thesymmetrical sequence consisting of the amplitude values of the elementsof the non-constant modulus column vector satisfies the followingrelationship:

$\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{M/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M/2})} + 1}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {even}} \right)};{{or}\text{}\left\{ {\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {odd}} \right)} \right.}} \right.$

Wherein, M is the length of the sequence; and a_(i) is the i^(th)amplitude value of the sequence, i is a natural number and 1≦i≦M.

In the embodiment of the present disclosure, alternatively, the sequenceconsisting of the amplitude values of the elements of the non-constantmodulus column vector and having symmetrical property includes twosymmetrical parts, and each symmetrical part is a geometric sequence.Specifically, for example, each symmetrical part is described in (10) or(11). It should be understood that the common ratio of the geometricsequence may be greater than 1, or smaller than 1, but not equal to 1.

Alternatively, the symmetrical sequence consisting of the amplitudevalues of the elements of the non-constant modulus column vectorincludes two symmetrical parts, and each symmetrical part is anarithmetic sequence. Specifically, for example, each symmetrical part isdescribed in (12) or (13). It should be understood that the commondifference of the arithmetic sequence may be greater than 0, or smallerthan 0, but not equal to 0.

In the embodiment of the present disclosure, alternatively, thenon-constant modulus precoding matrix is the product of a diagonalmatrix and a constant modulus matrix, wherein the diagonal elements ofthe diagonal matrix consist of the amplitude values of elements of thenon-constant modulus column vector. Specifically, for example, thenon-constant modulus precoding matrix has a structure described in (14)to (18).

Further, in the embodiment of the present disclosure, the amplitudevalues of the elements of the non-constant modulus column vector may beselected from a finite set, for example, the amplitude values of theelements are the products of the amplitudes of known modulation symbols(such as modulation symbols in 16QAM or 64QAM or 256QAM) and a commonfactor. The above-mentioned selection may reduce the implementationcomplexity of the eNB precoding operation.

The base station 700 according to the embodiment of the presentdisclosure may correspond to the base station eNB provided in theembodiment of the present disclosure, and the above-mentioned and otheroperations and/or functions of modules in the base station 700 are torealize the corresponding flow of the method 300 in FIG. 2, which is notredundantly described herein for the purpose of briefness.

Therefore, according to the base station of the embodiment of thepresent disclosure, the precoding matrix is determined from the codebookwith the non-constant modulus precoding matrix, and the non-constantmodulus precoding matrix has the non-constant modulus column vector ofwhich the amplitude values of the elements are symmetrical or partiallysymmetrical, so that the non-constant modulus precoding matrix mayadjust beam shape, thus antennas may focus power on a hotspot region, aload balance of a communication system may be effectively realized, andthe performance of the communication system may be improved.

In addition, the terms “system” and “network” may be exchanged with eachother for use herein. The term “and/or” herein is merely a correlationfor describing associated objects, and denotes that three relations mayexist. For example, A and/or B may denote three conditions that A existsalone, A and B coexist, and B exists alone. In addition, the symbol “/”herein generally denotes an “or” relation of the front and backassociated objects.

It should be understood that, in the embodiments of the presentdisclosure, “B corresponding to A” denotes that B is associated with Aand may be determined according to A. It should also be understood that,determining B according to A does not mean that B is determined onlyaccording to A, and B may also be determined according to A and/or otherinformation.

Those skilled in the art may realize that the units and algorithmicsteps of the examples described in conjunction with the embodimentsdisclosed in the present disclosure may be realized by electronichardware or computer software or the combination of computer softwareand electronic hardware. In order to clearly illustrate theinterchangeability of hardware and software, the composition and stepsof each example are already generally described according to functionsin the above-mentioned description. Whether these functions are executedin a hardware or software mode depends on the specific applications anddesign constraint conditions of the technical solution. For eachspecific application, the described functions may be realized byprofessionals using different methods, but this realization shall not beconsidered as going beyond the scope of the present disclosure.

Those skilled in the art to which the present disclosure pertains mayclearly understand that, for the purpose of convenience and briefness indescription, for the specific working processes of the above-describedsystems, devices and units, reference could be made to the correspondingprocesses in the embodiments of the aforementioned methods, and repeateddescription is not given here.

In the several embodiments provided by the present application, itshould be understood that the disclosed systems, devices and methods maybe realized in other modes. For example, the embodiments of theabove-described devices are only exemplary, for example, the division ofthe units is only a logic function division, other division modes may beadopted in practice, e.g., a plurality of units or components may becombined or integrated in another system, or some features may beomitted or are not executed. In addition, the displayed or discussedmutual coupling or direct coupling or communication connection may beindirect coupling or communication connection of devices or unitsthrough some interfaces, and may also be in electrical, mechanical orother forms.

The units illustrated as separate components may be or may not bephysically separated, and the components displayed as units may be ormay not be physical units, that is to say, the components may bepositioned at one place or may also be distributed on a plurality ofnetwork units. The objectives of the solutions of the embodiments of thepresent disclosure may be fulfilled by selecting part of or all of theunits according to actual needs.

In addition, in various embodiments of the present disclosure, thefunctional units may be integrated in one processing unit, or thefunction units may separately and physically exist, or two or more unitsmay be integrated in one unit. The integrated unit may be realized inthe form of hardware or in the form of software functional units.

When the integrated unit is realized in the form of software functionalunits and sold or used as independent products, the integrated unit maybe stored in a computer-readable storage medium. Based on such anunderstanding, the technical solution of the present disclosuresubstantially, or the part of the present disclosure making contributionto the prior art, or all or a part of the technical solution may beembodied in the form of a software product, and the computer softwareproduct is stored in a storage medium, which includes a plurality ofinstructions enabling computer equipment (which may be a personalcomputer, a server, or network equipment and the like) to execute all ofor part of the steps in the methods of the embodiments of the presentdisclosure. The aforementioned storage medium includes various mediacapable of storing program codes, such as a U disk, a mobile hard disk,a read-only memory (ROM, Read-Only Memory), a random access memory (RAM,Random Access Memory), a disk or an optical disk.

The above description is merely the specific embodiments of the presentdisclosure, but the protection scope of the present disclosure is notlimited thereto, any skilled who is familiar with this art could readilyconceive variations or substitutions within the disclosed technicalscope disclosed by the present disclosure, and these variations orsubstitutions shall be encompassed in the protection scope of thepresent disclosure. Thus, the protection scope of the present disclosureshall be subjected to the protection scope of the claims.

What is claimed is:
 1. A method for determining a precoding matrixindicator, comprising: receiving a reference signal set sent by a basestation; based on the reference signal set, selecting a precoding matrixfrom a codebook, the codebook at least comprising a non-constant modulusprecoding matrix, the non-constant modulus precoding matrix at leastcomprising a non-constant modulus column vector, amplitude values of atleast two elements of the non-constant modulus column vector forming asymmetrical sequence; sending a precoding matrix indicator to the basestation, the precoding matrix indicator corresponding to the selectedprecoding matrix.
 2. The method according to claim 1, wherein thesequence satisfies one of the following relationship:$\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{M/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M/2})} + 1}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {even}} \right)};{{and}\text{}\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {odd}} \right)};} \right.}} \right.$wherein, M is a length of the sequence; and a_(i) is a i^(th) elementamplitude value of the sequence, i is a natural number and 1≦i≦M.
 3. Themethod according to claim 1, wherein the symmetrical sequence comprisestwo symmetrical parts, and each symmetrical part is a geometricsequence.
 4. The method according to claim 1, wherein the symmetricalsequence comprises two symmetrical parts, and each symmetrical part isan arithmetic sequence.
 5. The method according to claim 1, wherein thenon-constant modulus precoding matrix is a product of a diagonal matrixand a constant modulus matrix, and diagonal elements of the diagonalmatrix consist of amplitude values of elements of the non-constantmodulus column vector.
 6. A method for determining a precoding matrixindicator, comprising: sending a reference signal set to a userequipment; receiving a precoding matrix indicator sent by the userequipment, the precoding matrix indicator corresponding to a precodingmatrix selected from a codebook by the user equipment based on thereference signal set, the codebook at least comprising a non-constantmodulus precoding matrix, the non-constant modulus precoding matrix atleast comprising a non-constant modulus column vector, and amplitudevalues of at least two elements of the non-constant modulus columnvector forming a symmetrical sequence.
 7. The method according to claim6, wherein the sequence satisfies one of the following relationship:$\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{M/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M/2})} + 1}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {even}} \right)};{{and}\text{}\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {odd}} \right)};} \right.}} \right.$wherein, M is a length of the sequence; and a_(i) is a i^(th) elementamplitude value of the sequence, i is a natural number and 1≦i≦M.
 8. Themethod according to claim 6, wherein the symmetrical sequence comprisestwo symmetrical parts, and each symmetrical part is a geometricsequence.
 9. The method according to claim 6, wherein the symmetricalsequence comprises two symmetrical parts, and each symmetrical part isan arithmetic sequence.
 10. The method according to claim 6, wherein thenon-constant modulus precoding matrix is a product of a diagonal matrixand a constant modulus matrix, and diagonal element of the diagonalmatrix consists of amplitude values of elements of the non-constantmodulus column vector.
 11. A user equipment, comprising: a receivingmodule, configured to receive a reference signal set sent by a basestation; a selecting module, configured to, based on the referencesignal set received by the receiving module, select a precoding matrixfrom a codebook, the codebook at least comprising a non-constant modulusprecoding matrix, the non-constant modulus precoding matrix at leastcomprising a non-constant modulus column vector, and amplitude values ofat least two elements of the non-constant modulus column vector forminga symmetrical sequence; a sending module, configured to send a precodingmatrix indicator to the base station, the precoding matrix indicatorcorresponding to the precoding matrix selected by the selecting module.12. The user equipment according to claim 11, wherein the sequencesatisfies one of the following relationship: $\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{M/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M/2})} + 1}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {even}} \right)};{{and}\text{}\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {odd}} \right)};} \right.}} \right.$wherein, M is a length of the sequence; and a_(i) is a i^(th) elementamplitude value of the sequence, i is a natural number and 1≦i≦M. 13.The user equipment according to claim 11, wherein the symmetricalsequence comprises two symmetrical parts, and each symmetrical part is ageometric sequence.
 14. The user equipment according to claim 11,wherein the symmetrical sequence comprises two symmetrical parts, andeach symmetrical part is an arithmetic sequence.
 15. The user equipmentaccording to claim 11, wherein the non-constant modulus precoding matrixis a product of a diagonal matrix and a constant modulus matrix, anddiagonal elements of the diagonal matrix consist of amplitude values ofelements of the non-constant modulus column.
 16. A base station,comprising: a sending module, configured to send a reference signal setto a user equipment; a receiving module, configured to receive aprecoding matrix indicator sent by the user equipment, the precodingmatrix indicator corresponding to a precoding matrix selected from acodebook by the user equipment based on the reference signal set, thecodebook at least comprising a non-constant modulus precoding matrix,the non-constant modulus precoding matrix at least comprising anon-constant modulus column vector, and amplitude values of at least twoelements of the non-constant modulus column vector forming a symmetricalsequence.
 17. The base station according to claim 16, wherein thesequence satisfies one of the following relationship:$\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{M/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M/2})} + 1}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {even}} \right)};{{and}\text{}\left\{ {{\begin{matrix}{{a_{1} \leq a_{2} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}} \\{{a_{M} \leq a_{M - 1} \leq},\ldots \mspace{14mu},{\leq a_{{({M + 1})}/2}}}\end{matrix}\left( {M\mspace{14mu} {is}\mspace{14mu} {odd}} \right)};} \right.}} \right.$wherein, M is a length of the sequence; and a_(i) is a i^(th) elementamplitude value of the sequence, i is a natural number and 1≦i≦M. 18.The base station according to claim 16, wherein the symmetrical sequencecomprises two symmetrical parts, and each symmetrical part is ageometric sequence.
 19. The base station according to claim 16, whereinthe symmetrical sequence comprises two symmetrical parts, and eachsymmetrical part is an arithmetic sequence.
 20. The base stationaccording to claim 16, wherein the non-constant modulus precoding matrixis a product of a diagonal matrix and a constant modulus matrix, anddiagonal elements of the diagonal matrix consist of amplitude values ofelements of the non-constant modulus column vector.